1. Field of the Invention
The present invention relates in general to sensor systems and more particularly, to a method for implementing rapid calibration of a beverage dispensing machine to ensure the quality of beverages such as soft drinks.
2. Description of the Prior Art
Without limiting the scope of the invention, the background set forth herein below is described in connection with sensing and controlling the quality of beverages such as soft drinks. It should be appreciated by one skilled in the art that the term beverages refers to a variety of fluids and other media, and that the principles of the present invention are applicable to a variety of media.
The dispensing of fountain beverages is presently generally accomplished using either premix systems in which a finished beverage is delivered to a proprietor from a bottler, and postmix systems in which flavored syrup is delivered to the proprietor and mixed with water at the point of delivery.
A premix system generally utilizes product containers filled with finished soft drinks that may be under carbon dioxide pressure. In these systems, the product is normally delivered to the consumer via a single orifice dispensing valve. Premix systems are also used in bottling plants that typically operate at extremely high flow rates. These systems are relatively expensive installations and are unsuitable for most typical restaurant settings.
A postmix system generally utilizes flavored syrup combined with carbonated or still water at a prescribed ratio and delivered through a dispensing valve at a fountain having passages for both syrup and water. The valve combines the syrup and water immediately before delivery into a cup on an individual serving basis. The valves are typically adjusted periodically to alter the mix ratio of the ingredients of the beverage.
In the restaurant industry, the valves that control the delivery of the beverage constituents are typically manually adjusted after a taste test of the finished beverage or a customer""s complaint, for example. The decision to alter the composition of the beverage is a highly subjective one, and is typically based on the operator""s subjective preference regarding the desired taste or sweetness of the beverage. In addition, the manual adjustment of the valves significantly lacks precision and accuracy. It is furthermore highly susceptible to human error, and is therefore inherently unreliable and inaccurate. The manual adjustments are also time-consuming and cumbersome.
Various attempts at maintaining a consistent ratio of the components of the beverages offered at a soft drink fountain dispenser have been made in the prior art. In one method, predetermined volumes of syrup and carbonated water are measured in a container called a Brixing cup. xe2x80x9cBrix,xe2x80x9d as understood by those skilled in the art, is the percent concentration of sugar. Proper Brixing is determined by ratio marks on the Brixing cup.
The Brixing method must be periodically repeated in order to account for any long term changes in the pressures or viscosities of the dispensed fluid. Short term variations in flow rates during a single dispensing operation, or between individual dispensing operations, cannot be accounted for by periodic manual adjustments.
In another method, the rate of flow of the syrup and carbonated water are measured with flow meters. The flow rates are adjusted and operate at a prescribed ratio. A flexible flow washer may be positioned in a flow line, and variations in fluid flow rate cause the opening of the washer to become enlarged or constricted. This method is flawed in that it does not account for factors contributing to variations in the accuracy of the mix ratio, such as changes in fluid viscosity. This method also lacks any significant degree of accuracy and is therefore unreliable.
U.S. patent application Ser. No. 09/549,287, entitled System and Method for Sensing and Controlling Beverage Quality, filed Apr. 14, 2000 by Melendez et al., and assigned to the assignee of the present invention, discloses among other things, use of a surface plasmon resonance sensor to implement a closed loop monitor and control system to maintain precise control of the beverage constituent concentrations associated with a product dispensed from a beverage dispensing machine. In practice, the beverage temperature is not well controlled and can vary greatly (e.g., 3xc2x0 C.-25xc2x0 C.). When this occurs, both the beverage temperature and the sensor temperature change unpredictably during operation, greatly affecting the refractive index measurements associated with a surface plasmon resonance sensor. Further, natural products from the beverage can foul the sensing surface of the sensor such that the sensor will generate erroneous readings.
Any inaccuracy in the ratio of the beverage constituents dispensed from a beverage dispensing machine results in inconsistency and undesirable variations in the quality and taste of the beverages. For example, dispensers that have poor accuracy and reliability may dispense a beverage that is too sweet or not sweet enough, or a carbonated soda that is flat. Variations from the desired mix accuracy also result in uneconomical use of the syrup.
In practice, the beverage temperature from dispensing system is not well controlled. It can vary from near 3xc2x0 C. to 25xc2x0 C. The dispense pattern, i.e., dispense time, the time between each dispense, is also irregular. These limitations, among others, can cause the beverage and sensor temperatures to change unpredictably during operation, which affects the refractive index sensor measurements associated with measuring the beverage quality. For example, the temperature change of a fixed optic sensor such as a surface plasmon resonance sensor will greatly affect refractive index reading. There is no existing method to measure this temperature change and, even if such a method existed, corrected for temperature-change-induced sensor variability would be difficult. Also, the temperature of beverage on the fixed optic sensor such as a surface plasmon resonance sensor will also affect refractive index reading because the measured refractive index of the beverage varies with temperature. Additionally, when the sensor is exposed to beverage, the nature product in the beverage will contaminate (i.e., foul) the sensor surface. These limitations, among others, can generate erroneous readings.
A need has therefore arisen for a method of sensing and controlling the quality of beverages that overcomes the limitations in the prior art. A method that provides for rapid calibration of the fixed optical sensor, to more accurately monitor beverage quality, would have great advantages over the prior art.
The present invention, according to one embodiment, comprises a method of automatically sensing and controlling beverage quality dispensed from a beverage dispenser, comprising the steps of a) supplying a first fluid, wherein the flow of the first fluid is controlled by a first valve; b) supplying a second fluid; c) mixing the first fluid and the second fluid (this mixture is called xe2x80x9cbeveragexe2x80x9d); d) calibrating a fixed optic sensor via passing a fluid with well-known properties, such as zero-Brix water, (dispensed by the beverage dispenser) onto the sensing surface of the fixed optic sensor; the zero-Brix water must be at the same temperature as the beverage; e) passing a sample of beverage onto the sensing surface of the fixed optic sensor subsequent to calibrating the fixed optic sensor; f) measuring one or more properties of the beverage; g) controlling the first valve based on the one or more properties to ensure proper beverage quality; h) repeating steps a-g to maintain a desired ratio of the fluids; and i) dispensing the mixture into a receptacle.